The present invention relates to a noble gas turbine combustor and, particularly, to a gas turbine combustor of Fe base casting alloy, Ni base casting alloy or Co base casting alloy, each of which has an excellent property against thermal fatigue, and a gas turbine employing the combustor.
A gas turbine combustor is made by cold forming of a plate, so that the plate is necessary to be made of an alloy which is excellent in hot working for forming a plate and in cold working for forming the combustor. Further, since the gas turbine combustor receives repeated heating and cooling by combustion gas of high temperature, it should be an alloy which has an excellent property against thermal fatigue.
The present inventors found that the larger the reduction of area in tensile property at room temperature is, the better the cold workability of an alloy is, and the larger the tensile proof strength, the reduction of area in tensile property and the creep rupture strength at high temperature are, the better the property against thermal fatigue becomes.
In conventional gas turbine combustors, Hastelloy X (0.1C-22Cr-9Mo-0.5W-1Co-19Fe-balance Ni) is used. However, in recent years, in order to improve the performance of gas turbines, combustion gas temperature tends to be raised. Therefore, the combustion gas temperature becomes higher than a heating temperature of the combustor liner. Hitherto, although the heating temperature of the combustion liner was less than 800.degree. C., it now exceeds 800.degree. C. Therefore, a sufficient property against thermal fatigue is not attained by the conventional Hastelloy X which has been used.
Since this alloy contains a lot of Mo, use of it for long time at a high temperature higher than 800.degree. C. precipitates a lot of brittle phase (inter metallic compound) and lowers remarkably the ductility of the alloy, whereby the alloy has such a defect that the property against thermal fatigue is low.
In the gas turbine combustor, fuel injected from a fuel nozzle is introduced into a combustion liner through a cap to be burnt there and the combustion gas is guided into turbine nozzles and blades through a transition piece. In the gas turbine combustor, the above-mentioned cap, liner and transition piece are exposed to high temperatures. Therefore, a heat resisting alloy is used for those structural members as mentioned above. In particular, since louver holes each are provided with sharp notches at both ends thereof, the louver hole portions are subjected to heat cycles of rapid heating and rapid cooling. Further, stress concentration occurs at their notch portions, so that cracks due to thermal fatigue are apt to occur at the notch portions in a case where an alloy which is easy to suffer heat embrittlement is used.
In order to improve power generation efficiency of a gas turbine power plant, a technique to use the gas turbine at high temperature is being studied. As the gas turbine is used at high temperature, it is desired to improve endurance temperature of parts of the gas turbine. By development of Ni base alloy, Co base alloy, etc. the endurance temperature of those heat resisting alloy have been raised. However, the endurance temperature is about 850.degree. C. at most at present.
On the other hand, ceramic material is more excellent in heat resistance than metal material. However, in a case where the ceramic material is used as the structural material, there is a problem of toughness, etc. Therefore, in order to meet the parts raised to high temperature, a lot of studies of methods in which the parts do not reach a high temperature have been conducted. As one of those methods, a study has been made of a method of cooling the parts. Further, as another method, there is a method of coating surfaces of metal members with ceramics of small thermal conductivity. Such coating is called a thermal barrier coating (hereunder, referred to as TBC). TBC is used, combined with various cooling methods, whereby the effect becomes larger. As an example, there is a report that temperature of a metal member which is a base member can be reduced by 50-100.degree. C. as compared with a metal member on which TBC is not applied. By using such a method, the reliability of structural members of high temperature gas turbines, etc. can be raised. On the other hand, there are technical problems of TBC such as adherence mechanism between a base material and a ceramic coating layer and reliability thereof since TBC combines a base material of heat resisting alloy and a ceramic coating layer which is different in values representative of physical properties. In particular, in gas turbines, etc. damages occur such as separation of the ceramic coating layer by thermal cycle due to starting and stoppage of the gas turbine.
Combustor linear material is disclosed in JP B 62-53583 and TBC thereof is disclosed in JP A 61-174385.
Operation temperature of gas turbines is increasing year by year as the efficiency of the gas turbines are made higher. In combustors also, it progresses to make the temperature higher, and material used therefor also is desired to be excellent in high temperature strength. However, current combustors each are produced by bending a rolled plate into a cylindrical shape and welding it. Since the rolled plate has small grain size, the creep strength at high temperature is low. Further, since cracks may occur during forging or rolling, it was impossible to add a lot of alloy components for strengthening the material of the rolled plate. Therefore, the upper limit temperature in practice has been 800.degree. C. Further, since the cylinder is produced by bending the rolled plate and welding it, the strength of the welded portion is lowered.
Even if TBC is utilized in order to prevent base metal temperature of gas turbine parts from becoming higher and reduce the temperature, the parts in which conventional TBC is utilized are impossible to sufficiently reduce the base metal temperature of the parts since the TBC is low in durability at high temperature.
An object of the present invention is to provide a gas turbine combustor and a gas turbine employing the combustor, in which an alloy having a high property against thermal fatigue at a higher temperature is used. In particular, an object of the present invention is to provide a gas turbine combustor and a gas turbine employing the combustor, in which an alloy having a creep rupture strength at 850.degree. C. for 10.sup.4 hours is 3 kg/mm.sup.2 or more is used.
Another object of the present invention is to provide a gas turbine combustor and a gas turbine, each of which has a thermal barrier coating (TBC) in which a joining force between a ceramic material and a base plate is stable for a long time and cracks and separation do not easily occur.
The present invention resides in a gas turbine combustor employing a combustor liner and a transition piece each of which is made cylindrical by casting without welding.
The combustor liner is made by precision casting or centrifugal casting and the transition piece is made by precision casting. The combustor liner has straight inner and outer peripheral surfaces. In particular, it is preferable to provide ring-shaped projections each peripherally extending on the outer peripheral surface for increasing cooling and its strength.
As material according to the present invention, any one of an Fe base casting alloy, Ni base casting alloy and Co base casting alloy is used. The Co base casting alloy comprises, by weight, 0.04-1.0% C, at most 1% Si, at most 2% Mn, 15-35% Cr, 0.5-20% W, at most 30% Ni and 35-60% Co, and it is preferable to contain at most 3% of at least one kind of MC type carbide forming elements such as Ti, Zr, Hf, V. In particular, preferable is an alloy including by weight 0.04-0.15% C, at most 1% Si, at most 2% Mn, 5-25% Ni, 20-30% Cr and 5-16% W, or an alloy including, in addition to the above elements, at least one element of 0.1-0.35% of Ti, Nb and Zr.
The Fe base casting alloy comprises by weight 0.04-1.0% C, at most 2% Si, at most 3% Mn, 15-35% Cr, 10-30% Ni, 30-50% Fe, and it is preferable to include further at most 3.0%, preferably, 0.1-1% of at least one element of the MC type carbide forming elements as mentioned above. In particular, preferable is a Fe base casting alloy comprising by weight 0.15-0.6% C, 0.5-2.0% Si, 0.5-3% Mn, 15-30% Ni, 20-30% Cr, 0.10-0.30% Ti and 0.10-0.35% Nb.
The Ni base casting alloy comprises by weight 0.04-0.5% C, at most 1% Si, at most 2% Mn, 15-35% Cr, 15-30% Co, at most 10% of at least one kind of W and Mo, 0.1-10% Ti, 0.1-5% Al and 35-55% Ni, and it is preferable for the alloy to include further at most 2% of at least one element of Ta, Nb, V, Hf and Zr. In particular, preferable is a Ni base casting alloy comprising by weight 0.05-0.15% C, at most 1% Si, at most 2% Mn, 20-30% Cr, 15-25% Co, 4-10% W, 1.5-3.5% Ti and 1.0-2.5% Al. In those alloys according to the present invention, it is preferable to make grain size equal to or larger than 100 .mu.m, preferably equal to or larger than 300 .mu.m in order to increase high temperature strength. Further, in order to prevent the strength of welding portions from lowering, it is necessary to make a cylindrical member without welding. In order to solve this, the cylindrical member is manufactured by centrifugal casting or lost wax precision casting. By casting it, a cylindrical member which has large grain size and no welding portion can be attained.
The present invention resides in a cylindrical gas turbine combustor burning injected fuel and leading the combustion gas into turbine nozzles, the inner cylindrical tube of the above-mentioned combustor being made of casting alloy comprising, by weight, 0.04-0.15% C, at most 1% Si, at most 2% Mn, 15-35% Cr and 0.5-20% W, or further including 15-40% Co, 0.1-5% Al, 0.1-5% Ti and 0.001-0.1% B, and bal. Ni of 20% or more, the casting alloy being Ni base casting alloy having substantially all austenitic phase. Further, it is preferable for the present invention to include, in the above-mentioned alloy, at least one selected from a group consisting of at most 0.5% rare earth metal, at most 3% Nb, at most 0.1% Mg and at most 0.5% Zr. In particular, 0.1-2% Al, 0.1-2% Ti and rare earth element 0.005-0.5% are preferable.
The present invention resides in a gas turbine which comprises a compressor, a combustor for producing combustion gas, using air compressed by the compressor and a turbine driven by the combustion gas and which is characterized in that a cylindrical portion of the combustor exposed to the combustion gas is made of austenitic Fe base casting alloy, Ni base casting alloy or Co base casting alloy.
Further, the present invention is characterized in that a compression ratio of the air is 15-20 and the temperature of the air is 350.degree. C. or more, the cylindrical portion of the combustor exposed to the combustion gas is provided with projections for cooling at its outer periphery and the outer peripheral portion is cooled by the compressed air so that its metal temperature becomes 800-900.degree. C., and the temperature of the combustion gas at an outlet of the combustor is 1400.degree. C. or more.
Further, the present invention is characterized in that a compression ratio of the air is 15-20 and the temperature of the air is 350.degree. C. or more, the outer peripheral portions of a combustor liner and a transition piece are cooled by the compressed air so that the metal temperature of the combustor liner and the transition piece, exposed to the combustion gas becomes 800-900.degree. C., the peripheral portion of the combustor liner is provided with projections for cooling, and the temperature of the combustion gas is 1400.degree. C. or more at an outlet of the combustor.
In the present invention, in a gas turbine which comprises a compressor having blades and static blades of at least 12 stages, and a turbine, integrated with the compressor and rotated at a high speed by combustion gas generated in a combustor, the compressor can be a compressor in which blades are formed in a rotor to be one piece as a whole, a compressor which has at least 12 stage blades planted on a rotor divided into a plurality of rotor pieces, at least 6 stage blades being planted on one rotor piece and each of the other rotor pieces having at most 3 stage blades planted thereon, or a compressor in which blades in each of the at least 12 stages are formed on one disc.
Further, in the present invention, as rotor material for the compressor, it is preferable to use Ni--Cr--Mo--V low alloy steel comprising by weight 0.15-0.40% C, at most 0.1% Si, at most 0.5% Mn, 1.5-2.5% Ni, 0.8-2.5% Cr, 0.8-2.0% Mo, 0.1-0.35% V and balance Fe and having full bainitic structure, for the one piece rotor, the rotor having each disc having stage blades, and the rotor in which blades are planted on divided rotor pieces. The above low alloy steel is further characterized by further including 0.0-0.1% of at least one kind of Nb and Ta.
Further, in a split rotor type compressor according to the present invention, the rotor divided into 6 rotor pieces on which at least 15 stage blades are mounted is preferable to be such that every 2 stage blades of blades from the first stage to the 8th stage are mounted on each rotor piece and every at least 3 stage blades of the 9th stage and the other stages are mounted on each of the other rotor pieces.
Compressor blades of the first stage and, if necessary, at least one stage from the 2nd stage to the 5th stage are preferable to be made of Ti alloy, and blades from the 2nd stage to the final stage are preferable to be made of martensitic stainless steel except for the blades of Ti alloy.
The present invention resides in a combined power generation system which is provided with a gas turbine, driven to rotate by combustion gas and a steam turbine, driven to rotate by steam generated in a waste heat recovery boiler recovering the heat of exhaust combustion gas from the gas turbine, and generates power by rotation of the gas turbine and the steam turbine, and which is characterized in that a combustor liner of the gas turbine is a casting of alloy selected from Fe base alloy, Ni base alloy and Co base alloy, a compression ratio of air compressed by a compressor is 15-20 and the temperature of the air is 400.degree. C. or more, a combustor outlet temperature of the combustion gas is 1400.degree. C. or more, the temperature of the combustion gas is 550-600.degree. C., and the steam turbine has a high and low pressure section integrated rotor shaft, the steam temperature being 530.degree. C. or more and thermal efficiency being 46% or more and/or the output thereof being 600 kW/(kg/S) or more.
Further, the present invention resides in a combined power generation system which has a gas turbine driven to rotate by combustion gas, and a steam turbine driven to rotate by steam generated in a waste heat recovery boiler recovering the heat of exhaust combustion gas from the gas turbine, and generates power by rotation of the gas turbine and the steam turbine, and which is characterized in that a combustor liner of the gas turbine is a casting of alloy selected from Fe base alloy, Ni base alloy and Co base alloy, a compressor of 15-20 stage blades is provided, the compression ratio of air compressed by the compressor is 15-20 and the temperature of the air is 400.degree. C. or more, the gas turbine has at least 3 stages, a combustor outlet temperature of the combustion gas is 1400.degree. C. or more, the temperature of the combustion gas is 550-600.degree. C. at an inlet of the waste heat recovery boiler and 130.degree. C. or less at an outlet of the boiler, and the steam turbine has blades planted on a high and low pressure section integrated rotor shaft, the final stage of the blades being 30 inches or more at a blade portion, the steam temperature being 530.degree. C. or more at a high pressure side inlet of the steam turbine and 100.degree. C. or less at a low pressure side outlet.
In the present invention, a combustor cylindrical liner and a transition piece are made of Fe base alloy, Ni base alloy or Co base alloy. By forming them by casting, high strength is attained. Further, since the cylindrical liner body has no welded portion, a strength decrease at the welded portion can be prevented. Since in the gas turbine combustor, the combustion gas temperature has been raised, exceeding 1300.degree. C., and becoming 1400.degree. C. and even 1500.degree. C., the combustor itself has been raised in temperature according to the elevation of the combustion gas temperature. Therefore, material of higher strength at a higher temperature is desired whereby it is possible to provide a structure having no welded portion in the barrel portion, and a structure thickened to 2 mm or less of the thickness and having no cooling hole is possible, whereby it is possible to reduce an amount of air used for cooling and improve the thermal efficiency.
C is contained in the amount of 0.04% or more in order to precipitate carbides during use at high temperature and raise proof strength and creep strength at high temperature. However, when C exceeds 1.0%, precipitation of carbides during use at high temperature is remarkable and reduction of area in tensile property at high temperature is lowered. In Co base alloy and Fe base alloy, it is preferable to be 0.04-1.0%, and 0.04-0.5% in Ni base alloy. In particular, it is preferable to be 0.05-0.2% in Ni base alloy, 0.15-0.35% in Fe base alloy and 0.15-0.35% in Co base alloy.
Cr effects solid solution into alloy and raises proof strength at a high temperature and creep strength. It is necessary to include at least 15% of the Cr in order to raise high temperature oxidation resistance and sulfidation corrosion resistance further. However, when Cr exceeds 35%, sigma phases precipitate and reduction of area in high temperature tensile test decreases. In particular, 18-30% is preferable in any case, and a more preferable range of Cr is 20-26%.
W, which is effective in Co base alloy and Ni base alloy, effects solid solution into alloy and raises remarkably the proof strength at high temperature. Further, creep rupture strength also is raised remarkably. However, when Cr exceeds 20% in Co base alloy and 10% in Ni base alloy, to the contrary, the proof strength is remarkably lowered. Further, cold workability and reduction of area in tensile property at high temperature are lowered, the latter because of precipitation of sigma phase. A preferable range of W is 5-16% in Co base alloy and 4-10% in Ni base alloy. Ni base alloy can contain W and Mo of equal amount, and it is preferable to contain the above-mentioned contents in total.
Co effects solid solution into Fe base alloy and Ni base alloy, and raises remarkably creep rupture strength at room temperature and a high temperature. However, when Co exceeds 30%, ductility at high temperature is lowered rapidly, whereby the reduction of area in tensile property at high temperature decreases. A preferable upper limit is 25%.
Al effects solid solution into alloy by addition of 0.1-5% to Fe base or Ni base alloy, and precipitates gamma prime phase during aging heat treatment at high temperature, thereby to raise tensile proof strength at high temperature and creep rupture strength. A preferable range is 1.0-2.5% Ni base alloy.
Addition of Ti, Zr, Hf or Nb of at most 3% to Fe or Co base alloy and 0.1-10% to Ni base alloy effects solid solution thereof into alloy, or precipitates gamma prime phase during aging heat treatment at high temperature to increase tensile proof strength at high temperature and creep rupture strength. However, when an addition amount exceeds 3% to Fe or Co base alloy, 10% to Ni base alloy, reduction of area in tensile property at high temperature decreases. A preferable range is 0.1-1.5% and more preferable 0.10-0.35% in Fe or Co base alloy, and 1.5-3.5% in Ni base alloy.
Fe is included upon addition of alloy elements in Ni base or Co base alloy. However, since it lowers creep rupture strength, it is better to reduce its content to the utmost. Even if it is contained, it is preferable to be 2% or less. At most 1% is preferable and at most 0.2% is more preferable.
Si and Mn are added as a deoxidizer. At most 2%, preferably at most 1.0% Si and at most 3%, preferably at most 2% Mn are added. However, addition exceeding the above-mentioned amounts lowers creep rupture strength, so that at most 2% Si and at most 3% Mn are added. In particular, addition of 0.2-0.6% Si and 0.4-1.0% Mn is preferable in any alloys of them.
B is segregated in austenitic grain boundaries by addition of a very small amount to increase creep rupture strength and ductility at high temperature. The effect is attained by addition of 0.001% or more, and when it exceeds 0.1%, hot workability and high temperature ductility are lowered. Therefore, 0.001-0.1% is preferable.
Mg and rare earth elements segregate in austenitic grain boundary to raise creep rupture strength. Further, Zr is a strong carbide former element, and addition of a small amount forms other carbides, for example, Ti carbide, etc. and increases creep rupture strength by multiplier action. However, the addition of an excessive amount of those elements decreases binding force of grain boundary and forms bulky carbide, whereby high temperature ductility decreases. Therefore, at most 0.1% Mg and at most 0.5% rare earth element, and in particular, 0.005-0.05% Mg and 0.005-0.1% rare earth element are preferable. The thickness of the combustor liner wall is preferable to be 1.0-5.0 mm, and more preferable to be 1.5-3.0 mm. The height of ring-shaped projections provided on the outer periphery of the combustor liner to strengthen the liner is preferable to be 1.0-3.0 mm. Total dimension of the thickness of the combustor liner and the height of the projections is preferable to be 4.0-6.0 mm. The thickness of the transition piece is preferable to be 2.0-7.0 mm and more preferable to be 3-5 mm. Further, the combustor liner is preferable to take such a construction that cooling of the liner by cooling air is carried out mainly only on the outer peripheral surface to increase the thermal efficiency.
In the present invention, it is preferable to provide, on the base material of the casting alloy having at least one kind of the above-mentioned Ni, Co and Fe as a main component, an alloy layer comprising at least one of Fe, Ni and Co as a main component, and Cr and Al and being more excellent in high temperature oxidation resistance and hot corrosion resistance than the above-mentioned base material, and a coating layer of ceramics having ZrO.sub.2 on the above-mentioned alloy layer, and form an oxide layer having Al as a main component on the boundary between the above-mentioned alloy layer and the above-mentioned ceramic coating layer. It is preferable that material constituting the above-mentioned ceramic coating layer includes ZrO.sub.2 as a main component, and at least one element having 5-10 wt % in total CaO, MgO and Y.sub.2 O.sub.3, and an alloy forming the above-mentioned alloy layer includes at least one of Fe, Co and Ni as a main component, 10-30 wt % Cr and 5-30 wt % Al, or further in addition thereto includes 0.1-5 wt % of at least one element of Hf, Ta, Y, Si and Zr. The ceramic coating layer is preferable to be 0.1-0.8 mm and the alloy layer 0.01-0.2 mm.